$\dfrac{5}{8} + \dfrac{3}{5} = {?}$
$ = {\dfrac{5 \times 5}{8 \times 5}} + {\dfrac{3 \times 8}{5 \times 8}} $ $ = {\dfrac{25}{40}} + {\dfrac{24}{40}} $ $ = \dfrac{{25} + {24}}{40} $ $ = \dfrac{49}{40}$